Saline soluble inorganic fibres

ABSTRACT

Thermal insulation is provided for use in applications requiring continuous resistance to temperatures of 1260° C. without reaction with alumino-silicate firebricks, the insulation comprises fibres having a composition in wt % 65%&lt;SiO 2 &lt;86%, MgO&lt;10%, 14%&lt;CaO&lt;28%, Al 2 O 3 &lt;2%, ZrO 2 &lt;3%, B 2 O 3 &lt;5%, P 2 O 5 &lt;5%, 72%&lt;SiO 2 +ZrO 2 +B 2 O 3 +5*P 2 O 5 , 95%&lt;SiO 2 +CaO+MgO+Al 2 O 3 +ZrO 2 +B 2 O 3 +P 2 O 5 . Addition of elements selected from the group Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y or mixtures thereof improves fibre quality and the strength of blankets made from the fibres.

[0001] This invention relates to saline soluble, non-metallic,amorphous, inorganic oxide, refractory fibrous materials. The inventionparticularly relates to glassy fibres having silica as their principalconstituent.

[0002] Inorganic fibrous materials are well known and widely used formany purposes (e.g. as thermal or acoustic insulation in bulk, mat, orblanket form, as vacuum formed shapes, as vacuum formed boards andpapers, and as ropes, yarns or textiles; as a reinforcing fibre forbuilding materials; as a constituent of brake blocks for vehicles). Inmost of these applications the properties for which inorganic fibrousmaterials are used require resistance to heat, and often resistance toaggressive chemical environments.

[0003] Inorganic fibrous materials can be either glassy or crystalline.Asbestos is an inorganic fibrous material one form of which has beenstrongly implicated in respiratory disease.

[0004] It is still not clear what the causative mechanism is thatrelates some asbestos with disease but some researchers believe that themechanism is mechanical and size related. Asbestos of a critical sizecan pierce cells in the body and so, through long and repeated cellinjury, have a bad effect on health. Whether this mechanism is true ornot regulatory agencies have indicated a desire to categorise anyinorganic fibre product that has a respiratory fraction as hazardous,regardless of whether there is any evidence to support suchcategorisation. Unfortunately for many of the applications for whichinorganic fibres are used, there are no realistic substitutes.

[0005] Accordingly there is a demand for inorganic fibres that will poseas little risk as possible (if any) and for which there are objectivegrounds to believe them safe.

[0006] A line of study has proposed that if inorganic fibres were madethat were sufficiently soluble in physiological fluids that theirresidence time in the human body was short; then damage would not occuror at least be minimised. As the risk of asbestos linked disease appearsto depend very much on the length of exposure this idea appearsreasonable. Asbestos is extremely insoluble.

[0007] As intercellular fluid is saline in nature the importance offibre solubility in saline solution has long been recognised. If fibresare soluble in physiological saline solution then, provided thedissolved components are not toxic, the fibres should be safer thanfibres which are not so soluble. The shorter the time a fibre isresident in the body the less damage it can do. H. Förster in ‘Thebehaviour of mineral fibres in physiological solutions’ (Proceedings of1982 WHO IARC Conference, Copenhagen, Volume 2, pages 27-55(1988))discussed the behaviour of commercially produced mineral fibres inphysiological saline solutions. Fibres of widely varying solubility werediscussed.

[0008] International Patent Application No. WO87/05007 disclosed thatfibres comprising magnesia, silica, calcia and less than 10 wt % aluminaare soluble in saline solution. The solubilities of the fibres disclosedwere in terms of parts per million of silicon (extracted from the silicacontaining material of the fibre) present in a saline solution after 5hours of exposure. The highest value revealed in the examples had asilicon level of 67 ppm. In contrast, and adjusted to the same regime ofmeasurement, the highest level disclosed in the Förster paper wasequivalent to approximately 1 ppm. Conversely if the highest valuerevealed in the International Patent Application was converted to thesame measurement regime as the Förster paper it would have an extractionrate of 901,500 mg Si/kg fibre—i.e. some 69 times higher than any of thefibres Förster tested, and the fibres that had the highest extractionrate in the Förster test were glass fibres which had high alkalicontents and so would have a low melting point. This is convincinglybetter performance even taking into account factors such as differencesin test solutions and duration of experiment.

[0009] International Patent Application No. WO89/12032 disclosedadditional fibres soluble in saline solution and discusses some of theconstituents that may be present in such fibres.

[0010] European Patent Application No. 0399320 disclosed glass fibreshaving a high physiological solubility.

[0011] Further patent specifications disclosing selection of fibres fortheir saline solubility include for example European 0412878 and0459897, French 2662687 and 2662688, PCT WO86/04807, WO90/02713,WO92/09536, WO93/22251, WO94/15883, WO97/16386 and U.S. Pat. No.5,250,488.

[0012] The refractoriness of the fibres disclosed in these various priorart documents varies considerably and for these alkaline earth silicatematerials the properties are critically dependent upon composition.

[0013] WO94/15883 disclosed a number of fibres that are usable asrefractory insulation at temperatures of up to 1260° C. or more. Thesefibres comprised CaO, MgO, SiO₂, and optionally ZrO₂ as principalconstituents. Such fibres are frequently known as CMS (calcium magnesiumsilicate) or CMZS ((calcium magnesium zirconium silicate) fibres.WO94/15883 required that any alumina present only be in smallquantities.

[0014] A drawback found in use of these fibres, is that at temperaturesbetween about 1300° C. and 1350° C. the fibres undergo a considerableincrease in shrinkage. Typically, shrinkages increase from about 1-3% at1200° C.; to, say, 5% or more at 1300° C.; to >20% at 1350° C. Thismeans that, for example, a temperature overrun on a furnace can resultin damage to the insulation and hence to the furnace itself.

[0015] A further drawback is that calcium magnesium silicate fibres canreact with, and stick to, alumina containing materials due to formationof a eutectic composition. Since aluminosilicate materials are widelyused this is a major problem.

[0016] WO97/16386 disclosed fibres that are usable as refractoryinsulation at temperatures of up to 1260° C. or more. These fibrescomprised MgO, SiO₂, and optionally ZrO₂ as principal constituents. Aswith WO94/15883, this patent required that any alumina present only bein small quantities.

[0017] While these fibres do not show the dramatic change in shrinkageevident in the fibres of WO94/15883, they do show a significantly highershrinkage at normal use temperatures typically having a shrinkage of3-6% over the range 1200° C.-1450° C. These fibres do not appear to havethe drawback of reacting with and sticking to alumina containingmaterials, however they tend to be difficult to make.

[0018] The applicants have invented a group of fibres that have a lowershrinkage across a range of temperatures than the fibres of WO97/16386,while having a higher onset of increase in shrinkage, and a more gentlechange in shrinkage, than the fibres of WO94/15883 and which also have areduced tendency to react with and stick to alumina.

[0019] Accordingly, the present invention provides thermal insulationfor use in applications requiring continuous resistance to temperaturesof 1260° C. without reaction with alumino-silicate firebricks, theinsulation comprising fibres having a composition in wt %

[0020] 65%<SiO₂<86%

[0021] MgO<10%

[0022] 14%<CaO<28%

[0023] Al₂O₃<2%

[0024] ZrO₂<3%

[0025] B₂O₃<5%

[0026] P₂O₅<5%

[0027] 72%<SiO₂+ZrO₂+B₂O₃+5*P₂O₅

[0028] 95%<SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅.

[0029] A preferred range of compositions is:

[0030] 72%<SiO₂<80%

[0031] 18%<CaO<26%

[0032] 0%<MgO<3%

[0033] 0%<Al₂O₃<1%

[0034] 0%<ZrO₂<1.5%

[0035] 98.5% <SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅.

[0036] A still more preferred range has the composition:

[0037] 72%<SiO₂<74%

[0038] 24%<CaO<26%

[0039] Additionally, the applicants have found that addition of smallamounts of lanthanide elements, particularly lanthanum, improves thequality of the fibres, particularly their length and thickness, suchthat improved strength results. There is a trade-off in terms ofslightly lower solubility, but the improved strength is of help,particularly in making such products as blankets, in which the fibresare needled to form an interlocking web of fibres.

[0040] Accordingly, the present invention comprises a silicate fibrecomprising:

[0041] 65%<SiO₂<86%

[0042] MgO<10%

[0043] 14%<CaO<28%

[0044] Al₂O₃<2%

[0045] ZrO₂<3%

[0046] B₂O₃<5%

[0047] P₂O₅<5%

[0048] 72%<SiO₂+ZrO₂+B₂O₃+5*P₂O₅

[0049] 95%<SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅.

[0050] where R is selected from the group Sc, La, Ce, Pr, Nd, Sm, Eu,Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, Y or mixtures thereof.

[0051] The preferred elements are La and Y. Preferably, to achievesignificant improvements in fibre quality, the amount of R₂O₃ is greaterthan 0.25%, more preferably >0.5%, and still more preferably >1.0%. Tominimise the reduction is solubility that occurs, the amount of R₂O₃ ispreferably <2.5%, still more preferably <1.5% by weight. Very goodresults are obtained for a fibre having the composition in wt %:

[0052] SiO₂: 73±0.5%

[0053] CaO: 24±0.5%

[0054] La₂O₃: 1.3−1.5%

[0055] Remaining components: <2%, preferably <1.5%

[0056] Further features of the invention will become apparent from theclaims in the light of the following illustrative description and withreference to the drawing FIG. 1 which is a graph of shrinkage againsttemperature of some fibres according to the present invention incomparison with some commercial fibres.

[0057] The inventors produced a range of calcium silicate fibres usingan experimental rig in which a melt was formed of appropriatecomposition, tapped through a 8-16 mm orifice, and blown to producefibre in a known manner. (The size of the tap hole was varied to caterfor the viscosity of the melt—this is an adjustment that must bedetermined experimentally according to the apparatus and compositionused).

[0058] The fibres were tested and the results for fibres that arepredominantly calcium silicate fibres with some MgO are shown in Table1, in which:

[0059] shrinkage figures are shown as measured on a preform of fibre bythe method (see below),

[0060] compositions are shown as measured by x-ray fluorescence withboron by wet chemical analysis,

[0061] total solubility in ppm of the major glass components after a 24hour static test in a physiological saline solution is shown,

[0062] specific surface area in m²g,

[0063] a qualitative assessment of fibre quality,

[0064] and an indication of whether the preform stuck to analuminosilicate brick (JM 28 bricks obtainable from Thermal CeramicsItaliana and having an approximate composition 70 wt % alumina and 30 wt% silica)

[0065] The shrinkage was measured by the method of manufacturing vacuumcast preforms, using 75 g of fibre in 500 cm³ of 0.2% starch solution,into a 120×65 mm tool. Platinum pins (approximately 0.1-0.3 mm diameter)were placed 100×45mm apart in the 4 corners. The longest lengths (L1 &L2) and the diagonals (L3 & L4) were measured to an accuracy of ±5 μmusing a travelling microscope. The samples were placed in a furnace andramped to a temperature 50° C. below the test temperature at 300°C./hour and ramped at 120° C./hour for the last 50° C. to testtemperature and left for 24 hours. On removal from the furnace thesamples were allowed to cool naturally. The shrinkage values are givenas an average of the 4 measurements.

[0066] The inventors found that those fibres having a silica contentless than 72% by weight tended to stick to the aluminosilicate brick.They also found that high MgO content fibres (>12%) did not stick (aspredicted from the properties of WO97/16386).

[0067] It is known that calcium silicate fibres having an intermediatelevel of MgO (12-20%) stick to aluminosilicate brick, whereas magnesiumsilicate fibres do not. Surprisingly, for the fibres of the presentinvention, such intermediate levels of MgO can be tolerated. Levels of<10% MgO, or <5% MgO give the non-sticking results required, but itappears preferable for refractoriness to have a maximum level of MgO at2.5% by weight, and more preferably the amount should be below 1.75% byweight.

[0068] Table 2 shows the effect of alumina and zirconia on these fibres.Alumina is known to be detrimental to fibre quality and the first threecompositions of Table 2 have over 2% Al₂O₃ and stick to aluminosilicatebrick. Additionally, increased alumina leads to lowered solubility.Accordingly, the inventors have determined 2% as the upper limit foralumina in their inventive compositions.

[0069] In contrast zirconia is known to improve refractoriness and Table2 shows that silica levels of below 72% can be tolerated if the amountof ZrO₂ is sufficient that the sum of SiO₂ and ZrO₂ is greater than 72%by weight. However, increasing zirconia lowers the solubility of thefibres in physiological saline solution and so the preferred level ofZrO₂ is less than 3%.

[0070] The effect of some other common glass additives is indicated byTable 3, which shows the effect of P₂O₅ and B₂O₃ as glass formingadditives. It can be seen that P₂O₅ has a disproportionate effect on thesticking properties of these compositions, as fibres with as low as67.7% SiO₂ do not stick to aluminosilicate brick.

[0071] B₂O₃ also has an effect with fibres having as low as 70.9% SiO₂not sticking. The inventors have determined that sticking toaluminosilicate brick tends not to occur for fibres meeting therelationship:

[0072] 72% <SiO₂+B₂O₃+ZrO₂+5*P₂O₅ .

[0073] The inventors have assumed a maximum level for B₂O₃ and P₂O₅ of5% by weight each.

[0074] Tables 1 to 3 show that minor amounts of other components may beincluded and the invention tolerates up to 5% of other ingredients, butpreferably these other ingredients amount to less than 2%, morepreferably less than 1%, since such other ingredients tend to make thefibres less refractory. (But see below for effect of specific lanthanideadditives).

[0075] The above results were obtained on an experimental rig, with allof the uncertainties that entails. Production trials of the mostfavourable appearing fibres were conducted on two separate sites toallow both blowing and spinning of the compositions to be tried. Table 4shows a selection of the results obtained (duplicates omitted) and showsthat a very usable fibre results. The fibres tested in the productiontrials had compositions falling in the approximate range

[0076] 72%<SiO₂<80%

[0077] 18%<CaO<26%

[0078] 0%<MgO<3%

[0079] 0%<Al₂O₃<1%

[0080] 0%<ZrO₂<1.5%

[0081] with 98.5% <SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅.

[0082] It can be seen that the compositions with an MgO level of greaterthan 1.75% tended to have a higher shrinkage at 1350° C. than those witha lower MgO level.

[0083]FIG. 1 shows in graphical form an important feature of the fibresof the invention and compares the shrinkage characteristics of the firstthree fibres and 5^(th) fibres of Table 4 (each referred to as SW613)with commercial fibres Isofrax® (a magnesium silicate fibre from UnifraxCorporation), RCF (a standard aluminosilicate refractory ceramic fibre),and SW607 Max™, SW607™, and SW612™ (calcium magnesium silicate fibresfrom Thermal Ceramics Europe Limited).

[0084] It can be seen that Isofrax® and RCF have a shrinkage that is inthe range 3-6% over the range 1200 to 1450° C. SW607 Max™, SW607™, andSW612™ have shrinkages in the range 2-5% at 1200° C. but increaserapidly after 1300° C. The fibres of the present invention have ashrinkage of less than 2% up to 1350° C., drift up to 5-8% at 1400° C.and accelerate thereafter.

[0085] The fibres of the present invention therefore have the advantageof a lower shrinkage than magnesium silicate, commercial calciummagnesium silicate, or RCF fibres at 1300° C.; commence their increasein shrinkage at a higher temperature than commercial calcium magnesiumsilicate fibres; have a shallower rise in shrinkage with temperaturethan commercial calcium magnesium silicate fibres; and do not stick toaluminosilicate brick in the way commercial calcium magnesium silicatefibres may.

[0086] The fibres can be used in thermal insulation and may form eithera constituent of the insulation (e.g. with other fibres and/or fillersand/or binders) or may form the whole of the insulation. The fibres maybe formed into blanket form insulation.

[0087] A problem found with the plain calcium silicate fibres describedabove was that the fibres tend to be short resulting in a poor qualityblanket. A means of producing better fibre for blanket was required andthe applicants conducted screening tests to investigate the effect onfibre quality of the addition of other elements as additives to thecomposition. It was found that lanthanide elements, particularly La andY improved fibre quality. La was determined to be the most commerciallyinteresting element and so after this initial screening test effortscentred on investigating the effect of La.

[0088] La₂O₃ was used as an additive in amounts of 0-4% to a fibrecomprising 73.5% SiO₂ and balance CaO and minor impurities to determinethe optimum amount. It was determined that addition of La₂O₃ improvedfiberisation while not reducing refractoriness. The fibres did not reactwith alumina bricks. However, at the highest levels of La₂O₃ thesolubility was reduced significantly. Accordingly a compromise level of1.3-1.5% La₂O₃ was used for further tests on the fibre composition.

[0089] To check and define the optimum formulation in terms ofrefractoriness and fiberisation for the lanthanum containing material, astudy was performed looking to the increase of silica from 67% to 78%SiO₂ in a material containing 1.3% La₂O₃ (ept constant), balanceCaO+minor impurities MgO and Al₂O₃.

[0090] Increasing silica increases the refractoriness of the fibre,giving lower shrinkage, higher melting point and decreases reaction withalumina at high temperature.

[0091] The best compromise between refractoriness and fiberisation wasfound for a composition of: SiO₂     73% CaO     24% La₂O₃ 1.3-1.5%Remaining impurities (Al₂O₃, MgO, others)   <1.5%

[0092] This composition was tried on production scale manufacturingblanket having the composition “With La” shown in Table 4 below.

[0093] It was confirmed that this composition produced better fibresthan an La free version.(“No La” in Table 4). The fibres still notreacting with alumina brick, and having good refractoriness.

[0094] Better fiberisation was observed and evaluated by looking to thetensile strength of 25 mm thick blanket having a density 128kg/m³. TABLE4 OXIDES No La With La Na₂O <0.05 0.18 MgO 0.89 0.46 Al₂O₃ 0.64 0.66SiO₂ 72.9 73.2 K₂O <0.05 0.08 CaO 25.5 23.6 Fe₂O₃ 0.11 0.14 La₂O₃ 0 1.3LOI 1025° C. 0.08 0.09 Total 100.1 99.7 Tensile strength 25-30 35-60128-25 blanket (kPa)

[0095] It can be seen that the addition of only 1.3% La₂O₃ results in aconsiderable improvement in tensile strength, indicating a much improvedfibre.

[0096] The applicants surmise that this effect of improving fiberisationis a viscosity or surface tension modifying effect applicable generallyto alkaline earth silicate fibres, and so the invention encompasses theuse of such additives generally in the amounts indicated above toimprove fiberisation of alkaline earth silicate fibres. TABLE 1 TotalSolu- Shrinkage %/24 hrs Composition (wt %) bility SSA JM 28 Comp. 1300°C. 1350° C. 1400° C. 1450° C. 1500° C. 1550° C. CaO SiO₂ P₂O₅ Al₂O₃ B₂O₃ZrO₂ MgO Na₂O K₂O TiO₂ Fe₂O₃ ZnO ppm m²/g Fibre Quality sticking CS01/C10.34 melted melted 35.00 62.40 0.83 0.56 0.30 0.15 0.24 230.0 0.33Coarse Stuck CS02/C 8.52 melted melted 33.00 63.80 0.77 0.51 0.40 0.140.22 199.0 0.45 Coarse Stuck CS01/D 5.14 32.90 64.60 0.80 0.48 0.26 0.150.18 199.1 0.37 Coarse Stuck CS01 2.60 4.34 melted 33.80 65.00 0.80 0.510.21 0.21 235.0 0.47 Coarse Stuck CS10 4.25 19.51 melted 33.00 65.400.76 0.52 0.24 0.15 0.21 199.8 0.30 Coarse Stuck CS10 cons 4.25 14.12melted 33.00 65.40 0.76 0.52 0.24 0.15 0.21 199.8 0.30 Coarse Stuck CS021.92 2.58 7.83 melted 31.90 66.50 0.77 0.49 0.31 0.20 218.0 0.59 CoarseStuck CS02/D 3.85 31.20 66.60 0.75 0.46 0.25 0.14 0.20 208.1 0.42 CoarseStuck CMS02 2.12 melted 18.30 66.90 0.31 14.40 0.17 0.14 213.2 0.42Coarse Stuck CMS02/B 2.35 7.02 melted 18.30 66.90 0.31 14.40 0.17 0.14Coarse Stuck CS03/D 11.87 28.90 69.30 0.70 0.44 0.19 215.0 0.54 CoarseStuck CMS03 2.95 melted 16.80 69.40 0.30 13.40 0.11 0.14 280.1 CoarseStuck CMS03/B 2.75 8.08 melted 16.80 69.40 0.30 13.40 0.11 0.14 CoarseStuck CS15 5.67 34.47 34.02 28.00 69.70 0.61 0.53 0.19 0.20 241.9 0.41Good fibre Stuck CS04/E 2.77 11.39 21.96 28.20 69.80 0.61 0.38 0.43 0.100.17 260.0 0.50 Lots of flake Stuck CS04/E cons 2.77 7.62 28.20 69.800.61 0.38 0.43 0.10 0.17 260.0 0.50 Lots of flake Stuck CS04 1.65 0.983.71 30.42 28.20 69.80 0.61 0.38 0.43 0.10 0.17 269.8 0.44 Lots of flakeStuck CMS04 2.35 melted 16.50 70.00 0.38 13.10 0.12 0.13 Coarse StuckCS12 2.35 9.10 31.40 26.90 70.70 0.66 0.41 0.39 0.12 0.18 211.3 0.55Good fibre Stuck CS12 cons 2.35 4.80 15.37 26.90 70.70 0.66 0.41 0.390.12 0.18 211.3 0.55 Good fibre Stuck CS16 9.37 35.35 34.37 27.20 71.000.61 0.49 0.16 0.17 283.1 0.55 Good fibre Stuck CS17 9.05 33.70 30.6426.60 71.40 0.62 0.48 0.17 0.17 228.2 0.71 Good fibre Stuck CS18 7.9232.00 30.02 26.20 71.60 0.75 0.49 0.20 0.18 248.8 0.71 Good fibre StuckCS19 4.84 27.36 26.41 26.40 71.60 0.73 0.48 0.21 0.19 248.2 0.63 Goodfibre Stuck CMS05 2.63 melted 15.10 72.00 0.97 11.40 0.23 0.12 125.2Coarse Stuck CMS05/B 3.31 8.11 14.10 15.10 72.00 0.97 11.40 0.23 0.12Coarse Stuck SACM01 4.01 3.56 4.79 3.17 78.00 1.60 17.00 0.21 160.0 0.37O.K fibre Not Stuck SACM02 3.51 5.04 76.50 1.62 14.80 0.12 0.20 206.30.33 O.K fibre Not Stuck SACM03 5.46 8.63 10.38 7.71 75.80 1.77 13.100.65 170.5 0.46 O.K fibre Not Stuck CSMg01 7.36 21.14 28.33 37.44 23.6072.90 0.61 2.61 0.11 0.16 223.6 0.66 Good fibre Stuck some shot CSMg032.24 7.17 12.61 20.20 75.70 0.57 2.61 0.20 0.18 231.3 0.38 Good fibreNot Stuck some shot CSMg02 7.14 12.13 16.17 27.03 21.60 75.20 0.54 2.590.14 210.6 0.63 Good fibre Stuck some shot CSMg07 7.38 20.47 23.00 73.800.49 1.81 0.17 250.1 0.42 O.k fibre Not Stuck CSMg06 6.23 25.18 12.3429.97 24.20 72.30 0.51 1.79 0.13 0.18 268.1 0.53 Good fibre Not StuckCSMg09 1.28 2.33 18.30 78.40 0.39 1.71 0.14 228.7 0.35 Shotty Not StuckCSMg08 2.86 8.24 9.70 31.43 20.50 76.50 0.44 1.65 0.16 257.2 0.43 Goodfibre Not Stuck CSMg10 1.85 1.80 17.30 79.40 0.28 1.61 0.15 248.3 0.22Coarse Not Stuck shotty CS Fe₂O₃ 01 1.94 8.72 19.79 26.24 22.60 74.400.57 0.72 0.23 0.44 279.9 0.49 O.k fibre Not Stuck CS Fe₂O₃ 05 3.4710.11 15.34 22.52 21.10 74.70 0.58 0.51 0.17 2.25 207.1 0.47 Shotty NotStuck CS Fe₂O₃ 02 1.43 3.64 21.90 74.80 0.56 0.50 0.22 0.65 285.5 0.30Shotty Not Stuck CS Al 03 2.18 8.47 15.15 22.38 22.30 74.60 1.03 0.410.18 0.15 0.48 Good fibre Not Stuck CS13 1.46 3.00 23.16 24.00 74.300.55 0.39 0.17 0.17 156.0 0.56 Shotty Not Stuck CS Fe₂O₃ 04 1.79 9.0314.51 19.78 21.60 74.90 0.52 0.39 0.16 1.47 239.7 0.41 Good fibre NotStuck CS Fe₂O₃ 03 2.43 12.43 20.53 24.24 21.90 74.70 0.52 0.38 0.21 1.06241.0 0.47 Good fibre Not Stuck CS05 1.21 1.79 4.14 melted 26.40 72.200.55 0.33 0.19 0.10 0.16 262.0 0.45 Lots of flake Not Stuck CS06/E 1.566.03 21.81 30.16 24.00 73.90 0.52 0.33 0.28 0.15 222.0 0.34 Lots offlake Not Stuck CS06/E cons 1.56 4.02 10.54 13.75 16.96 24.00 73.90 0.520.33 0.28 0.15 222.0 0.34 Lots of flake Not Stuck CS Al 02 1.48 2.4113.51 18.28 23.10 74.70 0.48 0.33 0.19 0.14 0.59 Good fibre Not StuckCS07/E 1.50 2.14 10.00 5.19 5.81 22.20 76.50 0.53 0.33 0.11 0.15 177.90.29 O.K fibre Not stuck CS14/B 2.22 6.23 22.60 75.00 0.58 0.30 0.120.17 137.3 0.55 Shotty Not Stuck CS08/E 2.03 1.34 3.10 7.72 19.50 78.900.70 0.27 0.16 0.18 160.0 0.32 Coarse Not Stuck CS06/B 2.66 melted 12.0024.30 75.00 0.39 0.26 0.15 0.12 172.0 0.55 Lots of flake Not Stuck

[0097] TABLE 2 Total Shrinkage %/24 hrs Solu- Total 1300° 1350° 1400°1450° 1500° 1550° Composition (wt %) bility SSA JM 28 SiO₂ ₊ Comp. C. C.C. C. C. C. CaO SiO₂ P₂O₅ Al₂O₃ B₂O₃ ZrO₂ MgO Na₂O K₂O TiO₂ Fe₂O₃ ZnOppm m²/g Fibre Quality sticking ZrO₂ CAS01 17.62 18.45 24.50 71.70 2.780.45 0.28 0.12 0.12 30.3 Coarse Stuck 72.15 CAS02 10.19 24.18 22.6073.50 2.52 0.91 0.25 0.11 0.15 20.1 Coarse Stuck 74.41 CAS03 5.42 14.6314.56 20.40 75.70 2.32 1.05 0.23 0.11 0.12 47.4 0.20 Coarse Stuck 76.75CS03/C 6.02 melted melted 31.50 65.60 0.83 0.14 0.47 0.36 0.14 0.23222.0 0.31 Coarse Stuck 65.74 CZrS02 15.01 31.08 27.40 65.80 0.70 3.850.40 0.37 0.12 0.19 107.2 0.39 Good fibre Stuck 69.65 CZrs03 7.39 30.6425.60 68.00 0.67 3.96 0.37 0.25 0.11 0.21 64.2 0.21 Good fibre Stuck71.96 CS11 4.96 19.95 34.81 29.00 68.90 0.75 0.13 0.47 0.30 0.13 0.19200.5 0.50 Coarse Stuck 69.03 CS11 4.96 11.42 22.67 29.00 68.90 0.750.13 0.47 0.30 0.13 0.19 200.5 0.50 Coarse Stuck 69.03 cons CZrS07 −0.2917.90 74.70 0.62 4.94 0.24 0.48 0.17 24.3 0.22 Very shotty Not Stuck79.64 CZrS06 melted 7.97 19.00 74.90 0.71 4.45 0.28 0.42 0.13 42.5 0.25Coarse Not Stuck 79.35 CZrS04 2.56 24.50 70.60 0.72 3.29 0.36 0.35 0.110.17 69.4 0.21 Good fibre Not Stuck 73.89 CS13 1.46 3.56 12.88 16.6028.58 24.30 73.30 0.57 0.73 0.31 0.26 0.20 156.0 0.56 Shotty Not Stuck74.03 cons CAS07 4.59 10.22 24.80 73.10 1.10 0.43 0.28 0.14 0.14 127.80.34 Coarse Not Stuck 73.53 CSMg04 1.76 2.94 16.70 79.40 0.38 0.43 2.350.18 243.0 0.09 Coarse Not Stuck 79.83 shotty CS08 1.24 1.30 1.74 3.3719.80 78.50 0.45 0.34 0.25 0.16 0.14 201.5 0.20 Lots of flake Not stuck78.84 CS05/B 0.86 1.53 5.56 26.00 72.00 0.62 0.33 0.31 0.22 0.15 182.00.34 Lots of flake Not Stuck 72.33 CS05/B 1.53 4.52 13.46 26.00 72.000.62 0.33 0.31 0.22 0.15 182.0 0.34 Lots of flake Not Stuck 72.33 consCS05/E 2.04 7.28 33.19 44.49 26.00 72.00 0.62 0.33 0.31 0.22 0.15 276.00.48 Lots of flake Not Stuck 72.33 CS05/E 2.04 8.19 20.34 25.44 28.0026.00 72.00 0.62 0.33 0.31 0.22 0.15 276.0 0.48 Lots of flake Not Stuck72.33 cons CS06 1.36 1.42 2.36 5.87 melted 23.40 73.30 1.77 0.27 0.320.14 0.14 244.6 0.32 Lots of flake Not Stuck 73.57 CSMg05 1.67 1.2616.40 79.80 0.35 0.14 2.46 0.13 237.2 0.11 Good fibre Not Stuck 79.94some shot CS07/B 0.86 1.50 2.17 10.00 15.00 22.20 76.60 0.52 0.12 0.260.11 0.12 104.0 0.23 Lots of flake Not Stuck 76.72 CS07/B 1.50 1.31 2.935.19 5.81 22.20 76.60 0.52 0.12 0.26 0.11 0.12 104.0 0.23 Lots of flakeNot Stuck 76.72 cons CS07 1.08 1.06 1.15 3.34 22.30 76.90 0.35 0.10 0.240.17 0.11 203.5 0.25 Lots of flake Not Stuck 77.00

[0098] TABLE 3 Total Total SiO₂ + Shrinkage %/24 hrs Solu- B₂O₃ + 1300°Composition (wt %) bility SSA Fibre JM 28 ZrO₂ + Comp. C. 1350° C. 1400°C. 1450° C. 1500° C. 1550° C. CaO SiO₂ P₂O₅ Al₂O₃ B₂O₃ ZrO₂ MgO Na₂O K₂OTiO₂ Fe₂O₃ ZnO ppm m²/g Quality sticking 5 * P₂O₅ CBS04 3.54 6.97 7.1618.00 77.90 0.43 2.03 0.70 0.31 0.17 0.24 64.0 0.16 Coarse Not stuck80.63 CBS03 3.47 10.32 16.43 20.40 75.20 0.48 2.12 0.84 0.33 0.18 0.1873.0 Coarse Not stuck 78.16 CPS02/ 4.02 21.40 75.00 1.54 0.48 0.32 0.130.16 336.0 0.27 Coarse Not Stuck 82.70 B CPS02 0.66 0.91 0.70 22.4074.60 1.61 0.29 0.26 0.90 0.27 0.21 0.11 349.6 0.10 O.K fibre Not Stuck83.81 CPS02 0.66 0.25 −0.21 22.40 74.60 1.61 0.29 0.26 0.90 0.27 0.210.11 336.8 0.10 Coarse Not Stuck 83.81 cons CPS21 3.04 23.00 74.10 0.420.61 0.45 0.38 0.10 0.20 188.0 0.41 O.K fibre Not Stuck 76.20 CBS05 4.149.98 14.71 21.20 73.90 0.54 3.11 0.32 0.16 0.17 117.0 0.35 Coarse NotStuck 77.01 CPS20 2.48 9.10 23.80 73.80 0.38 0.66 0.29 0.35 0.18 0.110.16 229.0 0.33 Good fibre Not Stuck 75.99 CPS20 2.48 6.21 11.94 17.3920.69 23.80 73.80 0.38 0.66 0.29 0.35 0.18 0.11 0.16 229.0 0.33 Goodfibre Not Stuck 75.99 cons CPS18/ 1.93 6.72 16.07 23.90 73.20 0.87 0.590.34 0.19 0.15 161.0 0.42 Shotty Not Stuck 77.55 B CPS17/ 2.39 6.3624.70 72.80 0.88 0.65 0.36 0.17 0.16 152.0 0.58 O.K fibre Not Stuck77.20 B CPS01/ 1.73 8.96 12.58 23.50 72.70 1.58 0.58 0.33 0.20 0.15275.0 0.34 Good fibre Not Stuck 80.60 B CPS01/ 2.05 11.86 5.87 6.1023.80 72.60 1.58 0.46 0.34 0.32 0.32 338.8 0.50 Coarse Not Stuck 80.50 CCBS02 4.93 18.32 23.28 22.90 72.60 0.70 2.16 0.30 0.33 0.24 0.15 85.0Good fibre Not stuck 75.06 CBS07 −0.29 6.10 14.69 24.30 72.20 0.38 1.380.84 0.27 0.18 0.13 90.0 0.32 Shotty Not Stuck 74.42 CPS01 2.29 1.250.15 23.90 71.50 1.52 0.48 0.90 0.95 0.29 0.48 0.10 286.3 0.13 O.K fibreNot Stuck 80.95 CPS01 2.29 1.25 0.15 23.90 71.50 1.52 0.48 0.90 0.950.29 0.48 0.10 338.8 0.13 Coarse Not Stuck 80.95 cons CPS17 2.86 25.2071.50 0.90 0.66 0.37 0.37 0.11 0.28 241.0 0.49 Shotty Not Stuck 76.00CPS19 2.87 19.23 26.90 25.50 71.50 0.48 0.64 0.15 0.39 0.44 0.11 0.18172.0 0.40 Good fibre Not Stuck 74.05 CBS01 3.79 21.92 25.20 70.90 0.622.13 0.84 0.41 0.12 0.20 101.2 0.45 Good fibre Not Stuck 73.87 CPS15/2.24 12.71 27.90 35.55 27.00 70.50 0.83 0.64 0.39 0.15 0.17 177.0 0.38Coarse Stuck 74.65 B CPS16 3.96 20.90 27.90 26.00 70.20 0.89 0.69 0.230.38 0.53 0.11 0.18 181.0 0.54 Coarse Not Stuck 74.88 CPS15 2.76 13.3728.94 26.70 70.00 0.93 0.69 0.43 0.38 0.12 0.20 166.6 0.61 Coarse NotStuck 74.65 CPS15 2.76 14.74 17.67 26.70 70.00 0.93 0.69 0.43 0.38 0.120.20 166.6 0.61 Coarse Not Stuck 74.65 cons CPS14/ 4.08 28.80 29.7067.70 0.90 0.69 0.46 0.19 0.10 0.22 153.9 0.32 O.K fibre Not Stuck 72.20B CS03 1.36 1.55 5.03 melted 30.20 67.60 0.15 0.87 0.42 0.21 0.11 0.18240.5 0.61 Coarse Stuck 68.35 CS03/ 3.81 18.22 melted melted 30.20 67.600.15 0.87 0.42 0.21 0.11 0.18 260.0 0.47 Coarse Stuck 68.35 E CS03/ 3.8113.67 28.02 30.20 67.60 0.15 0.87 0.42 0.21 0.11 0.18 260.0 0.47 CoarseStuck 68.35 E cons CPS13 6.92 4.00 38.52 30.20 65.70 0.93 0.70 0.47 0.540.13 0.20 163.8 0.44 O.K fibre Stuck 70.35 CPS14 1.90 13.10 melted 30.8064.80 0.99 0.80 0.48 0.30 0.13 0.21 153.9 0.47 O.K fibre Stuck 69.75CPS14 1.90 5.30 11.68 15.88 30.80 64.80 0.99 0.80 0.48 0.30 0.13 0.21153.9 0.47 O.K fibre Stuck 69.75 cons CPS12 8.72 5.93 melted 32.10 63.800.89 0.75 0.49 0.31 0.14 0.20 165.6 0.55 Lots of Stuck 68.25 flake CPS1115.72 10.06 melted 34.40 62.00 0.99 0.81 0.10 0.55 0.31 0.13 0.21 170.50.53 Good fibre Stuck 67.05

[0099] TABLE 4 Shrinkage %/24 hrs Composition (wt %) Comp. 1300 13501400 1450° 1500° 1550° C. CaO SiO₂ P₂O₅ Al₂O B₂O₃ ZrO₂ 50% YIELD 0.641.30 6.78 28.55 30.83 25.50 72.70 0.59 SPUN 0.38 0.77 5.48 30.54 40.3025.40 73.10 0.67 BLOWN 0.80 1.30 7.89 29.43 39.64 25.30 73.10 0.54Blanket 0.61 0.90 23.00 74.60 0.56 BAG 24 0.85 1.43 4.69 18.36 25.6923.18 75.18 0.66 BAG 7 0.57 0.84 2.22 22.32 26.70 24.26 73.95 0.63 BAG41 0.83 1.02 1.51 12.12 17.85 21.62 76.65 0.79 BAG 46 1.56 0.96 1.367.69 12.84 18.70 79.80 0.81 BAG 62 0.65 3.24 8.33 13.25 22.84 19.7476.25 0.47 0.82 No. 3 3.36 8.02 19.94 75.35 0.37 1.11 No. 4 2.54 8.1220.81 75.45 0.39 1.05 No. 5 1.96 6.55 20.61 75.28 0.36 0.99 Blanket 1st0.54 23.80 74.20 0.62 Blanket Last 1.13 1.37 6.00 16.21 28.76 melted25.01 72.89 0.57 Blanket 1st 1.28 1.79 2.56 27.17 25.11 23.80 74.20 0.62Blanket Last 1.06 1.35 1.71 21.38 31.51 25.01 72.89 0.57 Bulk Hi Speed1.52 1.81 13.71 24.15 24.56 24.90 72.20 0.72 Total Composition (wt %)Solubility Fibre JM 28 Comp. Mg Na₂ K₂O TiO₂ Fe₂O ZnO ppm SSA m²/gQuality sticking 50% YIELD 0.50 0.26 0.19 232.0 0.22 Very good Not StuckSPUN 0.54 0.18 254.0 0.23 Very good Not Stuck BLOWN 0.55 0.22 196.8 0.47Very good Not Stuck Blanket 0.43 0.22 0.12 0.17 240.7 0.16 Very good NotStuck BAG 24 0.42 0.17 300.0 0.23 Very good Not Stuck BAG 7 0.45 0.19117.0 0.16 Very good Not Stuck BAG 41 0.38 0.17 127.0 0.17 Very good NotStuck BAG 46 0.43 0.14 62.0 0.17 Very good Not Stuck BAG 62 2.27 0.1595.0 0.16 Very good Not Stuck No. 3 2.99 0.16 202.8 1.15 Very good NotStuck No. 4 2.87 0.16 210.2 0.61 Very good Not Stuck No. 5 2.70 0.16229.4 0.88 Very good Not Stuck Blanket 1st 0.77 205.2 0.41 Very good NotStuck Blanket Last 0.92 264.4 0.15 Very good Not Stuck Blanket 1st 0.77205.2 0.41 Very good Not Stuck Blanket Last 0.92 264.4 0.15 Very goodNot Stuck Bulk Hi Speed 0.82 267.5 0.15 Very good Not Stuck

1. Thermal insulation for use in applications requiring continuousresistance to temperatures of 1260° C. without reaction withalumino-silicate firebricks, the insulation comprising fibres having acomposition in wt % 72%<=SiO₂<86% MgO<=2.5% 14%<CaO <28% Al₂O₃<2% ZrO₂<3B₂O₃<5% P₂O₅<5% 72% <SiO₂+ZrO₂+B₂O₃+5*P₂O₅ 95%<SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅
 2. Thermal insulation as claimed inclaim 1, in which the amount of MgO present in the fibre is less than1.75%.
 3. Thermal insulation as claimed in claim 1, in which the amountof CaO is in the range of 18%<CaO<26%.
 4. Thermal insulation as claimedin claim 1, in which 98%<SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅.
 5. Thermalinsulation as claimed in claim 4, in which98.5%<SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅.
 6. Thermal insulation asclaimed in claim 5, in which 99%<SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅. 7.Thermal insulation as claimed in claim 1, having the composition:72%<SiO₂<80% 18%<CaO<26% 0%<MgO<2.5% 0%<Al₂O₃<1% 0%<ZrO₂<1.5% 98.5%<SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅.
 8. Thermal insulation as claimed inclaim 1, having the composition: 72%<SiO₂<74% 24% <CaO<26%
 9. A silicatefibre comprising: 65%<SiO₂<86% MgO<10% 14%<CaO<28% Al₂O₃<2% ZrO₂<3%B₂O₃<5% P₂O₅<5% 72% <SiO₂+ZrO₂+B₂O₃+5*P₂O₅ 95%<SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅ 0.1%<R₂O₃<4% where R is selected fromthe group Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, Yor mixtures thereof.
 10. A silicate fibre as claimed in claim 9, inwhich R is La or Y or mixtures thereof.
 11. A silicate fibre as claimedin claim 10, in which R is La.
 12. A silicate fibre as claimed in claim9, in which the amount of R₂O₃ is greater than 0.25%, morepreferably >0.5%, and still more preferably >1.0%.
 13. A silicate fibreas claimed in claim 9, in which the amount of R₂O₃ is <2.5%, preferably<1.5% by weight.
 14. A silicate fibre as claimed in claim 9, having thecomposition in wt %: 72%<SiO₂<80% 18%<CaO<26% 0%<MgO<3% 0%<Al₂O₃<1%0%<ZrO₂<1.5% 1% <R₂O₃<2.5%
 15. A silicate fibre as claimed in claim 14,in which R comprises La.
 16. A silicate fibre as claimed in claim 15,having the composition in wt %: SiO₂: 73±0.5% CaO: 24±0.5% La₂O₃:1.3−1.5% Remaining components: <2%, preferably <1.5%
 17. Thermalinsulation comprising silicate fibres as claimed in claim
 9. 18. Thermalinsulation comprising wholly fibres as specified in claim
 1. 19. Thermalinsulation as claimed in claim 1, in which the thermal insulation is inthe form of a blanket.
 20. Thermal insulation as claimed in claim 1, foruse in applications requiring continuous resistance to temperatures of1300° C. without reaction with alumino-silicate firebricks.
 21. Use asthermal insulation, of a body comprising fibres as specified in claim 1,in an application requiring continuous resistance to temperatures of1260° C. without reaction with alumino-silicate firebrick.
 22. Use asclaimed in claim 21, in an application requiring continuous resistanceto temperatures of 1300° C. without reaction with alumino-silicatefirebrick.
 23. A method of improving the fiberisation of alkaline earthsilicate fibres having a composition in wt % 65%<SiO₂, <86% MgO<10%14%<CaO<28% Al₂O₃<2% ZrO₂,<3% B₂O₃<5% P₂O₅<5% 72% <SiO₂+ZrO₂+B₂O₃+5*P₂O₅95% <SiO₂+CaO+MgO+Al₂O₃+ZrO₂+B₂O₃+P₂O₅ by inclusion in the components ofthe fibre of R₂O₃ in amounts ranging from 1% to 4% by weight, where R isselected from the group Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er,Tm, Yb, Lu, Y or mixtures thereof.
 24. A method as claimed in claim 23,in which R is La or Y or mixtures thereof.
 25. A method as claimed inclaim 24, in which R is La.